Manhole safety gratings

ABSTRACT

Systems and methods for making and using manhole safety gratings are described. Each safety grating includes a plate that has a first surface, a second surface, and a perimeter edge that extends between the two surfaces. The plate also defines a plurality of vents that extend between the first surface and the second surface. The plate can have any suitable shape or size that fits within the desired manhole. The plate can comprise any suitable material and be any suitable weight that provides the desired protection to the manhole. The safety gratings can therefore provide temporary safety for the manhole when they are used in place of permanent safety gratings. Other embodiments are described.

FIELD

This application relates generally to manholes and manhole covers. More specifically, this application relates to a temporary manhole safety grating and methods for making and using the same.

BACKGROUND

The term manhole or maintenance hole typically refers to the top opening of an underground utility vault that is used to house an access point for accessing and performing maintenance on underground and buried public utilities and other services. For instance, manholes often provide access to buried sewer lines, storm drains, natural gas lines, steam lines, telephone cables, electrical cables, traps, culverts, and cooling chambers. Additionally, while manholes can be located in any suitable location, they are often located in places that are subject to pedestrian and/or vehicle traffic (e.g., in a sidewalk, a street, etc.).

To protect manhole openings, manholes are often covered by a manhole cover, which is a plug that is designed to prevent accidental and/or unauthorized access to the manhole. Because many manhole covers are found in streets and sidewalks, and can therefore be exposed to heavy automobile and/or pedestrian traffic, such covers are often made from a relatively heavy and durable material, such as metal (e.g., cast iron) and/or a slab of precast concrete. In this regard, some conventional manhole covers can weigh between about 113 kilograms (kg) (e.g., about 250 pounds (lbs)) and about 136 kg (e.g., about 300 lbs).

SUMMARY

This application relates to manhole safety gratings. In particular, this application discusses systems and methods for making and using manhole safety gratings that are intended to be temporary in nature. Generally, each safety grating includes a plate that has a first surface, a second surface, and a perimeter edge that extends between the two surfaces. The plate also defines a plurality of vents that extend between the first surface and the second surface. The plate can have any suitable shape or size that fits within the desired manhole. The plate can comprise any suitable material and be any suitable weight that provides the desired protection to the manhole. The safety gratings can therefore provide temporary safety for the manhole when they are used in place of permanent safety gratings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description can be better understood in light of the Figures, in which:

FIG. 1A shows a top view of some embodiments of a circular manhole safety grating;

FIG. 1B shows a side view of some embodiments of the manhole safety grating;

FIG. 2 shows a top view of some embodiments of a square manhole safety grating;

FIG. 3 shows a side-cutaway view of some embodiments of the manhole safety grating disposed on a manhole cover receptacle;

FIG. 4 shows a top view of some embodiments of the circular manhole safety grating; and

FIG. 5 shows a side view of some embodiments of the manhole safety grating with a representative embodiment of a taper attached to a second surface of the grating.

The Figures illustrate specific aspects of the described manhole safety gratings and methods for making such gratings. Together with the following description, the Figures demonstrate and explain the principles of the structures, methods, and principles described herein. In the drawings, the thickness and size of components may be exaggerated or otherwise modified for clarity. The same reference numerals in different drawings represent the same element, and thus their descriptions will not be repeated.

DETAILED DESCRIPTION

The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan would understand that the described manhole safety gratings and associated methods of making and using the gratings can be implemented and used without employing these specific details. Indeed, the manhole safety gratings and associated methods can be placed into practice by modifying the illustrated devices and methods and can be used in conjunction with any other apparatus and techniques conventionally used in the industry. For example, while the description below focuses on methods for making and using the manhole safety gratings for manholes that release steam, the manhole safety gratings can be used on virtually any type of manhole, including manholes that provide access to sewer lines; storm drains; natural gas lines; telephone cables; electrical cables; drains; traps; cooling chambers; access points to a culvert, underground chambers; and/or any other suitable manhole.

When a conventional (or permanent) manhole cover has been removed from an opening of a manhole, the open manhole is often protected with one or more barricades, stanchions, traffic cones, manhole rails, telescopic rails, and/or other protective equipment. However, because the manhole itself is generally left open, a person, such as a worker, can still fall into the manhole if the person inadvertently slips, trips, or falls in proximity to the manhole. In this regard, because steam emitted from some open manholes can cause the surfaces surrounding such manholes to become wet and slippery, and because the released steam can reduce visibility, such manholes can be particularly dangerous when left open—even when other conventional protective equipment is employed.

The present application describes manhole safety gratings that can be used to temporarily cover a manhole opening when the permanent manhole cover is temporarily removed. While the described manhole safety gratings can comprise any suitable component that allows them to provide this function, FIG. 1A shows some embodiments in which the manhole safety grating 10 comprises a plate 15 that defines a plurality of vents 20. To provide a better understanding of the safety grating, the plate and vents are described below in more detail.

The plate 15 can serve any suitable purpose. Indeed, in some instances, the plate can be used to temporarily cover an open manhole to prevent people, animals, and other objects from accidentally falling into the manhole. Along these lines, the plate can also be configured to be easily placed over and removed from the manhole to allow for easy access to the manhole.

The plate can have any suitable characteristic that allows it to fulfill its intended purpose. In one example, FIG. 1B shows that the plate 15 has a first surface 25, a second surface 30, and a perimeter edge 35 that extends between the first and second surfaces. In this example, the first and second surfaces and the perimeter edge can have any suitable characteristic. Indeed, in some implementations, the first and second surfaces are substantially flat. In other implementations, however, the first and/or second surfaces can optionally be roughened and can optionally have raised and/or depressed surfaces (i.e., raised and/or depressed designs, writing, images, reinforcements, etc.). In such implementations, the roughened, raised, and/or depressed surfaces can perform any suitable function, including reinforcing the grating, improving the grating's aesthetics, and/or improving the traction across a surface of the safety grating.

In some implementations, the perimeter edge 35 can extend perpendicularly between the first surface 25 and the second surface 30. In other implementations, though, the perimeter edge can have any other suitable shape, including a rounded shape or a shape that tapers from the first surface to the second surface (e.g., where the second surface is smaller than the first surface). By way of illustration, FIG. 1B shows some embodiments in which the perimeter edge 35 is chamfered between the perimeter edge and the first surface 25 and between the perimeter edge and the second surface 30. While this chamfering may provide the safety grating with a variety of features, in some instances the chamfering facilitates seating the safety grating within a manhole cover receptacle.

From a top view of the first surface 25, the plate 15 can have any suitable shape that provides the needed safety for the manhole opening. In this regard, some examples of suitable shapes include shapes that are circular, ellipsoidal, square, rectangular, triangular, hexagonal, octagonal, polygonal, irregular, and any other suitable shape. Additionally, where the plate is shaped to have corners (e.g., where the plate is square, rectangular, etc.), the corners can come to a point or can be rounded. Thus, the safety grating 10 can be used to cover manhole openings having virtually any shape. By way of illustration, FIGS. 1A and 2 show some embodiments in which the plate 15 is substantially circular and square, respectively.

The plate 15 can be any suitable size that provides the needed safety for the manhole opening. Where the plate has a circular shape, the plate can have any suitable diameter (shown as length D in FIG. 1B). In another example, the plate can have any suitable width and length (shown as width W and length L, respectively, in FIG. 2). In this regard, because the diameter of a circular plate can be equal to the width as well as to the length of that plate, when the following discussion refers to the plate's width and length, the discussion may also be referring to the diameter of a circular plate. In some embodiments, the plate's width and length (or diameter) are each larger than a measurement selected from about 0.3 m (e.g., about 12 in), about 0.51 m (e.g., about 20 in), about 0.61 m (e.g., about 24 in), and about 0.76 meters (m) (e.g., about 30 in). In some embodiments, the plate's width and length (or diameter) are each smaller than a measurement selected from about 0.61 m (about 24 in), about 0.91 m (about 36 in), and about 1.1 m (about 44 in), and about 1.4 m (about 56 in).

The plate 15 can have a width W and length L (or diameter D) that each measure between any of the upper and lower measurements described herein. Indeed, where the plate has a circular shape, some implementations of the plate can have a diameter D between about 0.61 m (about 24 in) and about 1.1 m (about 44 in). In other implementations, the plate can have a diameter D of about 0.8 m±2.5 cm (about 31.5 in±1 in). Where the plate has a square, rectangular, or other shape, in some embodiments the plate's width W and length L can each range between about 0.61 m and about 1.22 m (about 24 in and about 48 in). In other embodiments where the plate is square, the plate can have a width W and a length L that are each about 0.81 m±5 cm (about 32 in±2 in). Similarly, where the plate is rectangular, some implementations of the plate have a width W of about 0.61 m (about 24 in) and length L selected from about 0.91 m (about 36 in) and about 1.22 m (about 48 in).

The plate 15 can be any suitable thickness that provides the needed safety for the manhole opening. In some embodiments, the plate can be as thin as a height H (shown in FIG. 1B) selected from about 2.5 cm (about 1 in), about 2.3 cm (about 0.9 in), and about 1.3 cm (about 0.5 in). Additionally, in some embodiments, the plate can be as thick as a height H selected from about 2.8 cm (about 1.1 in), about 3.8 cm (about 1.5 in), and about 6.5 cm (about 2.5 in). In other embodiments, the plate can have any suitable thickness between any combination of the upper and lower height H ranges provided above. For instance, the plate can have a height H of about 2.5 cm±0.5 cm (about 1 in±0.2 in).

In some configurations, the plate 15 can be sized to overlap a retaining lip in a manhole cover receptacle. In this manner, the safety grating can be prevented from falling into the manhole when the safety grating is located in the receptacle. By way of non-limiting illustration, FIG. 3 shows some embodiments in which an edge of the safety grating 10 overlaps a retention lip 40 in a manhole cover receptacle 45 by a distance shown as O.

Where the plate 15 overlaps one or more retention lips 40 (or an inner diameter) of a manhole cover receptacle 45, the plate can overlap each lip by any suitable length. Indeed, in some embodiments, at one or more of its edges, the plate is sized to overlap a retention lip in a corresponding manhole cover receptacle by a distance that is as great as an overlap distance O (shown in FIG. 3) selected from about 3.8 cm (about 1.5 in), about 2.5 cm (about 1 in), about 1.3 cm (about 0.5 inch), and about 0.6 cm (about 0.25 in). In some embodiments, this distance can be as small as an overlap distance O selected from about 0.3 cm (about 0.1 in), about 0.5 cm (about 0.2 in), about 1.3 cm (about 0.5 in), and about 1.5 cm (about 0.6 in). Accordingly, one or more edges of the plate can overlap a retention lip in the manhole cover receptacle by any amount between a combination of the upper and lower overlap distance O provided above. For instance, one or more edges of the plate can overlap a retention lip by about 1.91 cm±0.25 cm (about 0.75 in±0.1 in).

As mentioned above, the safety grating 10 also comprises one or more vents 20. Such vents can perform any suitable function, including allowing relatively large amounts of steam to be released from a manhole opening when the grating covers the opening; allowing a coupling end of a valve key to pass through at least one of the vents so that the key's user can operate one or more valves in the manhole while the grating is in place; allow cables, hoses, and other objects to extend into the manhole while the grating covers the manhole's opening; or any combination of these functions.

The safety grating 10 can comprise any suitable type of vent 20, including one or more key vents, utility vents, and/or other type of holes that extend between the plate's first 25 and second 30 surfaces. The key vent may refer to a vent that is sized and shaped to allow the coupling end of a standard valve key to pass through the vent. The utility vent may refer to a vent that opens from the plate's perimeter edge and that extends into the plate so that one or more cables, hoses, or other objects can extend into a manhole when the manhole is covered with the safety grating.

Where the safety grating 10 comprises one or more key vents, the grating can comprise any suitable number of key vents. By way of example, the grating can comprise 1, 2, 3, 4, . . . 20, or even more key vents. For instance, FIG. 4 shows some embodiments in which the grating 10 comprises 13 key vents 50.

The key vents 50 can have any suitable configuration. In some embodiments, the key vents can be any suitable shape, including square, rectangular, circular, ellipsoidal, triangular, hexagonal, octagonal, polygonal, irregular, or combination(s) of these shapes. For instance, FIG. 4 shows some embodiments in which the key vents 50 are substantially square shaped.

In those embodiments where the key vent 50 comprise a shape having one or more corners (e.g., a square, triangle, etc.), the corners may be pointed or the corners may be rounded, as shown in FIG. 4. Indeed, corners that come to a point may act as stress risers in the plate.

The key vents 50 can be any suitable size that allows the coupling end of a standard valve key to pass therethrough. Indeed, in some embodiments, where the coupling end of a valve key measures (from its face view) about 9.5 cm by about 9.5 cm (about 3.75 in by about 3.75 in). For example, the key vents 50 can have a minimum width X and height Y (shown in FIG. 4) that are each greater than a measurement each selected from about 9.7 cm (about 3.8 in), about 10.2 cm (about 4 in), and about 10.8 cm (about 4.25 in). In another example, the vents can have a maximum width X and height Y that are each less than a measurement selected from about 20.3 cm (about 8 in), about 15.2 cm (about 6 in), and about 12.7 cm (about 5 in). In fact, the key vents can have a width X and length Y that are each selected from a range found between any suitable combination of the aforementioned minimum and maximum measurements provided above. For example, some embodiments of the key vents have a width X and height Y that are each about 11.4 cm±0.64 cm (about 4.5 in±0.25 in).

The key vents 50 can be configured in any suitable location and/or pattern in the safety grating 10. For example, one or more key vents can be defined towards the center of the plate 15, towards the plate's perimeter edge 35, and anywhere in between the plate's center and perimeter edge. And since the key catch for a valve in a manhole may be disposed in a variety of locations, in some embodiments the grating 10 contains key vents in a variety of locations throughout the plate to allow the user to choose to insert the valve key into a key vent that is aligned with a desired key catch. By way of illustration, FIG. 4 shows some embodiments in which the grating 10 defines several key vents 50 that are disposed in a plurality of different locations throughout the grating. More specifically, FIG. 4 shows some embodiments in which the plate 15 defines at least one key vent 50 in each quarter section of the plate.

Where the safety grating 10 comprises one or more utility vents, the grating can comprise any suitable number of utility vents. For example, the grating can comprise 1, 2, 3, 4, 5, or more utility vents. By way of illustration, FIG. 4 shows an embodiment in which the grating 10 comprises a single utility vent 60.

The utility vent 60 can have any suitable configuration that allows one or more cables (e.g., electrical cables for lighting, tools, etc.), hoses (e.g., for pumps, vacuums, etc.), tools, and other objects to pass through, without being threaded through, the utility vent when the grating 10 is seated on a manhole cover receptacle. The utility vent can be any suitable shape that allows it to open from the grating's perimeter edge 35. For example, the utility vent can be somewhat circular, square, rectangular, ellipsoidal, polygonal, triangular, irregular, or any other suitable shape. FIG. 4 shows some embodiments in which the utility vent 60 has a rectangular appearance. While FIG. 4 shows some embodiments in which the corners 65 of the utility vent 60 are rounded, in other embodiments the corners of the utility vent can come to a point.

The utility vent 60 can be any suitable size that allows it to function as described herein. In some embodiments, the utility vent extends into the plate 15 far enough to allow for cables and/or hoses to curve from the exterior surface of the manhole down into the manhole. Indeed, in some embodiments, the utility vent extends into the grating as much as a length Z (as shown in FIG. 4) selected from about 25.4 cm (about 10 in), about 20.3 cm (about 8 in), about 15.2 cm (about 6 in), and about 14 cm (about 5.5 in). In some embodiments, the utility vent extends into the grating as little as a length Z selected from about 5.1 cm (about 2 in), about 7.6 cm (about 3 in), about 10.2 cm (about 4 in), and about 12.7 cm (about 5 in). Accordingly, the utility vent can have a length Z that is selected from a range found between any combination of the aforementioned minimum and maximum lengths provided above. For example, some embodiments of the utility vent have a length Z that is about 12.7 cm±1.3 cm (about 5 in±0.5 in).

The utility vent 60 can also have any suitable width (or diameter) A that allows it to function as described herein. In some embodiments, the utility vent has a width as small as a measurement selected from about 9.7 cm (about 3.8 in), about 10.2 cm (about 4 in), and about 10.8 cm (about 4.25 in). In some embodiment, the utility vent has a width A as large as a measurement selected from about 20.3 cm (about 8 in), about 15.2 cm (about 6 in), and about 12.7 cm (about 5 in). Accordingly, the utility vent can have a width A that is selected from a range found between any suitable combination of these minimum and maximum measurements. For example, some embodiments of the utility vent have a width A that is about 11.4 cm±0.64 cm (about 4.5 in±0.25 in).

Where the safety grating 10 comprises more than one utility vent 60, the utility vents can be disposed in any suitable location with respect to each other. For instance, the utility vents can be disposed opposite to each other, or in any other suitable location. Further, where the grating comprises more than one utility vent, each vent may be the same size and shape or a different size and/or shape.

The grating's various vents (e.g., key vents 50, utility vents 60, and/or any other vents) can account for any suitable percent of the overall surface area of the plate's first surface 25. Indeed, in some embodiments, the vents account for more than a percentage selected from about 25%, about 30%, about 35%, about 40%, about 55%, about 65%, and about 70% of the first surface's total surface area. In some embodiments, the vents account for a less than a percentage selected from about 80%, about 70%, about 60%, about 50%, and about 40% of the first surface's total surface area. Thus, the vents can account for any suitable surface area range between any suitable combination of the upper and lower percentages provided above. For example, the vents can account for between about 25% and about 65%, between about 30% and about 60%, or between about 35% and about 40% of the first surfaces total area.

In addition to these components, the safety grating 10 can comprise any other suitable component or be configured with any other characteristic. In one example, the plate's second surface 30 can comprise a taper, raised supports, and/or other objects that reinforce the grating, help center the grating in a manhole cover receptacle, and/or help retain the grating within the opening of a manhole. The taper, raised supports, and/or spacers can have any suitable characteristic, including some embodiments in which the taper 70 simply comprises a tapered portion of material that is attached to the plate's second surface 30 as shown in FIG. 5.

In another example, the safety grating 10 can optionally comprise a color or marking that indicates that caution should be used when maneuvering around the grating. For instance, the grating can comprise a neon yellow, neon green, or any other suitable color that is likely to catch the attention of people in proximity to the grating. Accordingly, such people can be warned that the safety grating does not necessarily have the characteristics (e.g., carrying capacity) of a permanent manhole cover.

The safety grating 10 can comprise any suitable material that allows it to function as described herein. In some embodiments, the material(s) that are used to create the grating (the grating material) allow the grating to support a person and prevent that person from falling into a manhole covered by the grating. In some instances, the grating material allows the grating to support a dead weight having a mass selected from at least about 90.7 kg about 200 lbs), about 136 kg (about 300 lbs), and about 168 kg (about 370 lbs). In some embodiments, the grating material can be electrically insulative. In other embodiments, the grating material also allows the grating to have a long-term maximum service temperature above the temperature of steam that is emitted from a manhole. In these embodiments, the grating material has a long-term maximum service temperature that is greater than a temperature selected from about 93° C. (about 200° F.), about 100° C. (about 212° F.), about 110° C. (about 230° F.), and about 121° C. (about 250° F.).

Some examples of suitable grating materials include polymers, metals, ceramics, glasses, resins, resinoids, or combinations thereof. In some embodiments, the grating materials comprise non-metal and non-concrete materials. For instance, the grating material can comprise a polymer, such as a nylon polymer, a high density polyethylene (e.g., QUADRANT EPP® high density polyethylene), a thermoplastic, or combinations thereof. Where the grating material comprises a nylon polymer, the grating material can comprise any suitable nylon polymer, including polyamide 6 (e.g., QUADRANT EPP® NYLATRON® GSN nylon type 6 oil and MoS₂ filled cast). Indeed, in some embodiments, the grating comprises or consists of polyamide 6.

The safety grating 10 can have any suitable weight that allows it to function as described herein. For example, when the safety grating has a diameter greater than about 0.56 m (about 22 in) (or a width and length that are each more than about 0.56 m), the grating can weigh less than a weight selected from about 22.7 kg (about 50 lbs), about 13.6 kg (about 30 lbs), about 11.3 kg (about 25 lbs), about 9.1 kg (about 20 lbs), and about 6.8 kg (about 15 lbs). Indeed, in some embodiments in which the grating has a diameter of about 0.8 m (about 31.5 inches), the grating weighs less than 11.3 kg (about 25 lbs) (e.g., about 9.1 kg±1 kg).

The manhole safety grating 10 described herein can be made in any manner that forms the structures described. By way of example, the plate 15 and vents (e.g., vents 50 and 60) can be formed through a process involving molding, extruding, casting, cutting, etching, stamping, drilling, bonding, routering, and/or any other suitable process.

The described safety grating 10 can be used in any suitable manner. In one example, the grating is used along with other protective equipment to protect a manhole opening. For instance, the grating can be used with one or more barricades, stanchions, traffic cones, manhole rails, and/or any other known or novel manhole protective equipment. Accordingly, the safety grating can be protected from pedestrian and vehicle traffic. In another example, when the grating 10 is being used with a manhole system having multiple openings that have their permanent manhole covers removed, one opening can be left uncovered to allow workers to enter and exit the manhole without obstruction, while the described safety grating can be placed over the other manhole opening(s). In still another example, the safety grating may be used where a user (e.g., a worker) is present to ensure that the safety grating is not treated like a conventional permanent manhole cover.

The manhole safety grating 10 may have several features. First, because the safety grating is intended to be temporary in nature and to be used in restricted work areas, the safety grating may not be required to comply with standard codes and specifications for conventional manhole covers (e.g., the NYC DOB code and AASHTO M 306-07 “Standard Specification for Drainage, Sewer, Utility, and Related Castings”). Accordingly, the safety grating can be made from lightweight materials, have a relatively large amount of its surface area devoted to vents, be easy to remove from a manhole cover receptacle, and otherwise vary from standard manhole cover requirements. Second, because the safety grating 10 can hold the weight of a large person, the grating can prevent a person from falling through a manhole opening covered by the grating.

A third feature is that since the safety grating 10 can be relatively lightweight, the safety grating can easily be transported, placed on, and removed from a manhole opening. As a result of the grating's ease of use, the grating may be readily used to protect people from falling into open manholes.

A fourth feature is that since the vents (e.g., vents 50 and 60) can account for a relatively large percentage of the area of the safety grating's first surface 25, the safety grating can allow relatively large amounts of steam to pass through the grating. As a result, the safety grating can protect the manhole opening while still allowing large amounts of steam to be vented from the manhole to improve visibility within the manhole.

In addition to any previously indicated modification, numerous other variations and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of this description, and appended claims are intended to cover such modifications and arrangements. Thus, while the information has been described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred aspects, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, form, function, manner of operation and use may be made without departing from the principles and concepts set forth herein. Also, as used herein, the examples and embodiments, in all respects, are meant to be illustrative only and should not be construed to be limiting in any manner. 

1. A manhole safety grating, comprising: a plate having a first surface, a second opposing surface, and a perimeter edge disposed between the first surface and the second surface, wherein the plate contains multiple vents that extend between the first surface and the second surface and the vents comprises a key vent having a width greater than about 9.5 centimeters and a length greater than about 9.5 centimeters.
 2. The safety grating of claim 1, wherein the vents account for more than about 25% of an area of the first surface.
 3. The safety grating of claim 1, wherein the safety grating weighs less than about 22 kilograms.
 4. The safety grating of claim 1, wherein the safety grating comprises a polymer.
 5. The safety grating of claim 4, wherein the polymer comprises a high density polyethylene polymer or a nylon polymer.
 6. The safety grating of claim 1, further comprising a utility vent that opens from the perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge.
 7. The safety grating of claim 1, wherein vents comprise 2 or more key vents.
 8. A manhole safety grating, comprising: a plate having a first surface, a second opposing surface, and a perimeter edge disposed between the first surface and the second surface; wherein the plate contains multiple vents that extend between the first surface and the second surface and the vents comprise a utility vent that opens from the plate's perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge.
 9. The safety grating of claim 8, wherein the vents account for more than about 30% of an area of the first surface.
 10. The safety grating of claim 8, wherein the safety grating weighs less than about 22 kilograms.
 11. The safety grating of claim 8, wherein the safety grating comprises a nylon polymer.
 12. A manhole safety grating, comprising: a plate having a first surface, a second opposing surface, and a perimeter edge disposed between the first surface and the second surface; wherein the plate contains multiple vents that extend between the first surface and the second surface and wherein the safety grating weighs less than about 13.6 kilograms.
 13. The safety grating of claim 12, wherein the vents account for more than about 30% of an area of the first surface.
 14. The safety grating of claim 12, further comprising a utility vent that opens from the perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge.
 15. The safety grating of claim 12, wherein the safety grating comprises a polymer.
 16. The safety grating of claim 15, wherein the polymer comprise a high density polyethylene polymer or a nylon polymer.
 17. The safety grating of claim 12, wherein the safety grating weighs less than about 11 kilograms.
 18. A manhole safety grating, comprising: a circular plate having a first surface, a second opposing surface, and a perimeter disposed between the first surface and the second surface; wherein the plate contains multiple vents that extend between the first surface and the second surface, the vents comprising multiple key vents each having a width greater than about 9.5 centimeters and a length greater than about 9.5 centimeters, and the vents account for more than about 30% of an area of the first surface; and wherein the safety grating weighs less than about 22 kilograms.
 19. The safety grating of claim 18, further comprising multiple key vents in a quarter section of the plate.
 20. The safety grating of claim 18, wherein the safety grating comprises an electrically insulative polymer.
 21. The safety grating of claim 20, wherein the polymer comprises a high density polyethylene polymer and a nylon polymer.
 22. The safety grating of claim 18, further comprising a utility vent that opens from the perimeter edge and extends into the plate more than about 5 centimeters from the perimeter edge.
 23. The safety grating of claim 18, wherein the first surface and the second surface are substantially free from raised surfaces.
 24. A method for using a temporary safety grating for a manhole, the method comprising: removing a permanent safety grating from the top of a manhole; and placing a temporary safety grating on the top of the manhole, the temporary grating comprising: a circular plate having a first surface, a second opposing surface, and a perimeter disposed between the first surface and the second surface; wherein the plate contains multiple vents that extend between the first surface and the second surface, the vents comprising multiple key vents each having a width greater than about 9.5 centimeters and a length greater than about 9.5 centimeters, and the vents account for more than about 30% of an area of the first surface; and wherein the temporary grating weighs less than about 22 kilograms.
 25. The method of claim 24, further comprising passing a key through the plate using the key vent. 